We have collected DNA and extensive phenotypic information on families with type 2 diabetes mellitus in Finland. Full genome scanning has identified regions of chromosomes 20, 22, 11, X, 6, and 3 that appear to harbor susceptibility genes. Fine mapping with closely spaced SNP markers is underway on chromosomes 20 and 22 to seek evidence for association. For that purpose, we have established the technique of MALDI-TOF mass spectrometry for SNP genotyping, and successfully demonstrated its application to DNA pools. Using this methodology, we have also confirmed an association of the Pro12Ala variant of the PPARG gene with type 2 diabetes, and are investigating a number of other candidate genes.